Heat olive oil in a skillet over medium heat. Add the chopped onion and sauté for about 3 minutes until softened. Then add the minced garlic and cook for 1 minute until fragrant.
Stir the diced tomatoes, cooked quinoa, thawed corn, and drained beans into the skillet. Add oregano, cumin, paprika, salt, and black pepper.
Spoon into peppers, sprinkle with cheese, and arrange in a baking dish. Bake uncovered for 30 minutes or until the peppers are tender and the cheese is melted.